Let's say a {glistener elf} was enchanted with {lifelink} and pumped with a {giant growth} dealing -4-4 counters on creature. Would life be gained? Is it redundant?
702.89c (http://imtgapp.com/forum/index.php?action=imtg;area=rule;number=702.89c): Damage dealt to a creature by a source with infect isn't marked on that creature. Rather, it causes that many -1/-1 counters to be put on that creature. See rule 119.3.
Damage is still dealt, just not marked as usual. You gain life. (Note that infect does not cause loss of life for a player hit by the creature).